1. Field of the Invention
The present application relates to a thermistor, and more particularly to a thermistor with high hold current value at high temperature.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Because the resistance of conductive composite materials having a positive temperature coefficient (PTC) characteristic is very sensitive to temperature variation, it can be used as the material for current sensing devices, and has been widely applied to over-current protection devices or circuit devices. The resistance of the PTC conductive composite material remains extremely low at normal temperature, so that the circuit or cell can operate normally. However, when an over-current or an over-temperature event occurs in the circuit or cell, the resistance instantaneously increases to a high resistance state (e.g., at least 102Ω), so as to suppress over-current and protect the cell or the circuit device.
PTC conductive composite material may include one or more crystalline polymers and conductive filler. The polymer may be usually polyolefin such as polyethylene, while the conductive filler may be carbon black. However, PTC conductive composite material having carbon black cannot obtain high hold current due to insufficient thermal mass and high resistance. When temperature rises, the hold current of the PTC conductive composite material will be tremendously decreased. Therefore, it cannot meet the requirements for protection to large-current secondary batteries.